For the most part, Windows 11 needs a computer from 2017 or more recent. By October 2025 when support for Windows 10 ends, that means computers more than 8 years old won't be supported. I do have a computer with a 6th generation processor that will be left behind (purchased in 2016), it's already moved to the living room where it is running Steam. In principle, I could use it for network rendering, but I don't think it would be worth the trouble, and in another two years it will be even more out of date. (In fairness, I might give it more though if the new computer was slower.)

For the developers, they are already doing cross-platform development, so I'm sure that helps, but if you look at the delays in getting Mac support updated, and assume Linux would add a similar amount of additional work, my personal guess is that there is not enough demand to justify taking that development time away from functionality.